Centrifugal thickener

ABSTRACT

The present invention relates to a centrifugal thickener comprising a machine housing, which includes a rotatable thickening cylinder and feed and discharge means for the slurry. The invention is characterized in that the feed means is a pipe axially projecting through one end of the machine housing, and that the discharge means is rotatably connected with the thickening cylinder and axially movable in relation to the same.

United States Patent Inventors Appl. No.

Filed Patented Assignee All Torsten Okvist Berghult, Skarblacka;

Nils 010i Nilsmar, Stalrlngen, Kallhall, both of Sweden Sept. 17, 1968 Sept. 28, 1971 Maskln A B N.A. Eie

Bandhagen, Sweden CENTRIFUGAL THICKENER 7 Claims, 5 Drawing Figs.

US. Cl

Int.

Field of Search [56] References Cited UNlTED STATES PATENTS 2,232,770 2/1941 Buddeberg 210/376 X 3,221,879 12/1965 lrving 210/376X Primary Examiner-Rueben Friedman Assistant Examiner-T. A. Granger Attorney- Pierce, Schefiler & Parker ABSTRACT: The present invention relates to a centrifugal thickener comprising a machine housing, which includes a rotatable thickening cylinder and feed and discharge means for the slurry. The invention is characterized in that the feed means is a pipe axially projecting through one end of the 'machine housing, and that the discharge means is rotatably connected with the thickening cylinder and axially movable in relation to the same.

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CENTRIFUGAL THICKENER This invention relates to thickening means for slurrics of different type, pulp, reject etc. and relates particularly to a continuous thickener operating by assistance of centrifugal force.

Water extractor means for slurry and the like are previously known and they usually are drum thickeners and screw thickeners. Thickening means heretofore used have to operate with several thickening steps, because the dry content of the concentrated material is relatively low in the first step. Owing to the extensive machine equipment thus required, the conventional thickening means have proved to be very bulky and, besides, expensive both in an initial and operation cost respect.

The present invention has as its object to eliminate or substantially reduce the drawbacks of conventional thickeners, and it relates to a centrifugal thickener comprising a machine housing, which includes a rotatable thickening cylinder and feed and discharge means for the slurry. The invention is characterized in that the feed means is a pipe axially projecting through one end of the machine housing, and that the discharge means is rotatably connected with the thickening cylinder and axially movable in relation to the same.

The invention will be described in greater detail in the following, with reference to the accompanying drawings.

FIG. 1 shows a longitudinal section through a centrifugal thickener according to the invention.

FIG. 2 shows a longitudinal section through the discharge means according to the invention.

FIG. 3 shows a cross section through one-half of the discharge means.

FIG. 4 shows a side view of the centrifugal thickener with drive mans.

FIG. 5 shows a longitudinal section through an extended centrifugal thickener according to the invention.

As appears from the drawings, a preferred embodiment of a centrifugal thickener according to the present invention substantially comprises a machine stand 1 with two upwardly extending bearing brackets 2, which support a stationary machine housing 3 comprising a rotor 4. Said rotor in its turn supports a thickening cylinder 11 in which a discharge means 17 is mounted so as to be able to be moved reciprocally. The rotor 4 preferably is supported on a tubular rotor shaft 5 by two end plates 6, which are rigidly connected with one another by peripheral axially extending stays 7. The rotor supporting shaft 5 is provided with inner tubular shaft journals 8 and 9 outwardly projecting through each end of the machine housing 3 and rotatably mounted in bearings 10 outside of the machine housing.

The thickening cylinder 11 is substantially shorter than the rotor and rigidly connected with the same. It comprises substantially two end rings 12 projecting outside of the periphery of the rotor, and two semicylindric perforated strainer plates 13, which are supported on a frame mounted between the end rings 12. For supporting the relatively thin strainer plates, radially projecting support rings 14 are mounted on the outside of the thickening cylinder. Those parts of the thickening cylinder end rings which project outside of the periphery of the rotor are provided with peripheral sealing flanges 15, which cooperate with correspondingly designed sealing flanges 16 in the machine housing.

The discharge means or discharger 17 reciprocating in the thickening cylinder 11 is slightly longer than the thickening cylinder and substantially comprises a plurality of parallel, annular plates 18 spaced from and rigidly connected with one another, between which plates axial walls 19 are provided adjacent the inner surface of the thickening cylinder and inclined to the direction of rotation. The discharger is slidably supported on the rotor shaft 5 by means of two annular end plates 20, the axial motion of the discharger opposite guided by slide engagement with the stays of the rotor 4 and effected by the assistance of a control rod 21 slidably mounted in the second 9 of the tubular shaft journals. The rod 21 is driven by a hydraulic engine outside of the machine housing via a coupling at its outer end. At its inner end the rod 21 is provided with a suitable through hole 22, through which a locking pin is inserted which locks one of the end plates 20 of the discharger to the rod 21. For this purpose the tubular shaft journal 9 and the rotor shaft 5 are provided with suitable axial slots.

The first tubular shafi journal 8 constitutes the inlet pipe for the slurry to be thickened and extends substantially to the center of the rotor 4 and'is at its inner end formed with shovelshaped distributing members 23, which distribute the ingoing slurry relatively uniformly around the inner periphery of the thickening cylinder 11 and between the plates 18 of the discharger 17. An annular end wall 24 in the rotor shaft 5 prevents the slurry from penetrating into the space between the inner wall of the rotor shaft and the shaft journal 8, and a circular wall 25 prevents the slurry from flowing in the opposite direction in the rotor shah.

The thickening cylinder 11, as already mentioned, is substantially shorter than the rotor 4 and it practically covers only a'central portion in the latter, the length of said portion being approximately half the rotor length. The thickening cylinder is locked against axial displacement, and centrally below the same an outflow shaft 26 for the outflow water is provided. The thickening cylinder is sealed against the remaining parts of the machine housing by its end plates 12 and the sealing flanges 15 formed at the periphery of said plates.

The centrifugal thickener according to the present invention operates as follows: The rotor 4 and thereby the thickening cylinder 11 and discharger 17 are rotated by a motor mounted outside of the machine housing 3. Simultaneously a control means for the discharger is actuated so as to cause the discharger to reciprocate continuously in the rotor, in such a manner, that in the one end position it has its one half outside of one end of the thickening cylinder and in the other end position it has its other half outside of the other end of the thickening cylinder. The slurry, which is distributed relatively uniformly along the inner periphery of the thickening cylinder and between the plates of the discharger, is pressed by action of the centrifugal force against the inner surface of the thickening cylinder whereby part of its water content flows out through holes in the cylinder. The press effect of the centrifugal force is improved in that the walls 19 mounted axially between the plates 18 of the discharger are inclined to the direction of rotation and thereby produce a wedge-shaped cavity between themselves and the thickening cylinder, into which cavity the slurry is pressed by the rotation force and there is thickened additionally by the wedge effect.

The plates 18 of the discharger, along their peripheral edges, are provided with sealing strips, which slidably abut to the inside of the thickening cylinder and upon the axial motion of the discharger scrapingly take along the slurry, so that between the discharger strokes no residues collect. In the lower side of the machine housing discharge shafts 27 for thickened slurry are provided between the ends of the thickening cylinder and the end walls of the housing. The slurry, thus, is collected along the inner surface of the thickening cylinder and is thickened during the rotation. During all this time the plates 18 of the discharger 17 scrapingly take along slowly the thickened slurry out through the ends of the thickening cylinder, the slurry falling down into the discharge shaft 27 and being collected below the discharger, while the outflow water flows down through the central shaft 26. By the extension of the centrifugal thickener shown in FIG. 5 and the associated simple reconstruction a doubling of its capacity has been obtained in a cheap way.

A centrifugal thickener of the type described is highly effective and with a small energy consumption normally dry contents of about 25 percent are achieved. In tests even dry contents of up to 30 percent have been obtained. It is relatively cheap to manufacture and very cheap to operate. it is easy to dismantle for cleaning and repair and can operate fully automatically.

We claim:

1. Centrifugal thickener for pulp, slurry and like materials, comprising a machine housing;

a rotor mounted for rotation within the housing;

a thickening cylinder comprising two semicylindrical perforated strainer plates mounted on longitudinal stays on the rotor at substantially the central portion thereof;

feed and discharge means for the slurry, said feed means being a pipe axially projecting into the machine housing through one end thereof, and said discharge means being rotatable by the rotor and axially movable in relation to the thickening cylinder.

2. Centrifugal thickener according to claim 1, said means inclt'iding a plate discharger being rotatably connected with the rotor for rotating the same, and in which said discharger, at its axial end positions, projects with substantially half its length outside of one or the other end of the thickening cylinder for discharging slurry into a discharge shaft provided inside of each end of the machine housing.

3. Centrifugal thickener according to claim 2, in which the feed pipe projects in along the center of the plate discharger substantially to the central portion of the thickening cylinder.

4. Centrifugal thickener according to claim 3, in which the mouth of the feed pipe is provided with shovels rotating in the direction of the plate discharger for imparting to the slurry fed in a rotary motion and to reduce its impact force against the longitudinal walls mounted between the discharger plates.

5. Centrifugal thickener according to claim 2, characterized in that the outer diameter of the plate discharger is sufficiently great for enabling the outer periphery of the plates scrapingly to take along with it slurry along the wall of the thickening cylinder.

6. Centrifugal thickener according to claim 2, in which the plates of the plate discharger are formed with two or more recesses at their outer periphery, into which recesses the iongitudinal stays in the rotor engage for moving the plate discharger in the direction of rotation, while allowing it to perform an axial motion in relation to the rotor.

7. Centrifugal thickener according to claim 2, in which the rotor is supported by a tubular shaft and first and second tubular shaft journals provided in said shaft and projecting out through the end walls of the machine housing, said first shaft journal being the feed pipe for the slurry while said second shaft journal includes an axially slidable control rod for axial motion of the plate discharger. 

1. Centrifugal thickener for pulp, slurry and like materials, comprising a machine housing; a rotor mounted for rotation within the housing; a thickening cylinder comprising two semicylindrical perforated strainer plates mounted on longitudinal stays on the rotor at substantially the central portion thereof; feed and discharge means for the slurry, said feed means being a pipe axially projecting into the machine housing through one end thereof, and said discharge means being rotatable by the rotor and axially movable in relation to the thickening cylinder.
 2. Centrifugal thickener according to claim 1, said means including a plate discharger being rotatably connected with the rotor for rotating the same, and in which said discharger, at its axial end positions, projects with substantially half its length outside of one or the other end of the thickening cylinder for discharging slurry into a discharge shaft provided inside of each end of the machine housing.
 3. Centrifugal thickener according to claim 2, in which the feed pipe projects in along the center of the plate discharger substantially to the central portion of the thickening cylinder.
 4. Centrifugal thickener according to claim 3, in which the mouth of the feed pipe is provided with shovels rotating in the direction of the plate discharger for imparting to the slurry fed in a rotary motion and to reduce its impact force against the longitudinal walls mounted between the discharger plates.
 5. Centrifugal thickener according to claim 2, characterized in that the outer diameter of the plate discharger is sufficiently great for enabling the outer periphery of the plates scrapingly to take along with it slurry along the wall of the thickening cylinder.
 6. Centrifugal thickener according to claim 2, in which the plates of the plate discharger are formed with two or more recesses at their outer periphery, into which recesses the longitudinal stays in the rotor engage for moving the plate discharger in the direction of rotation, while allowing it to perform an axial motion in relation to the rotor.
 7. Centrifugal thickener according to claim 2, in which the rotor is supported by a tubular shaft and first and second tubular shaft journals provided in said shaft and projecting out through the end walls of the machine housing, said first shaft journal being the feed pipe for the slurry while said second shaft journal includes an axially slidable control rod for axial motion of the plate discharger. 